A variety of elastomeric seals have been developed to protect structural expansion joints against leakage as the joint opening varies with changes in ambient operating conditions. Such joint seals include numerous forms of peripheral and internal truss structures which cause the seal to function in a particular manner to seal a joint during the expansion and contraction of the associated structural members.
In addition to withstanding frequent flexure due to the expansion and contraction of the associated structural members, it is also frequently necessary for such joint seals to withstand transient deck loads imposed by vehicular or pedestrian traffic. Thus, it is necessary that such joint seals have sufficient strength and flexibility to elastically recover from both transverse movement and vertical flexure.
It is commonly required that such joint seals be compressible up to at least 50% of their uncompressed or free-state form without losing their ability to reexpand to their installed shape and size when such compressive forces are diminished.